Field of the Invention
The present invention concerns the technical field of diffusion imaging, in particular to a stimulated echo magnetic resonance sequence scanning method and apparatus for heart diffusion imaging.
Description of the Prior Art
Magnetic resonance (MR) imaging is an imaging technology involving biomagnetics and nuclear spin which has advanced rapidly with the development of computer technology, electronic circuit technology and superconductor technology. It uses a magnetic field and radio-frequency (RF) pulses to induce oscillation of precessing hydrogen nuclei (i.e. H+) in human tissue, to generate RF signals, which are processed by a computer to form an image.
Diffusion is random, irregular motion of molecules, being one of the ways in which substances are transported in the body, and is also called Brownian motion. The tissue structure of an organism has an effect on the diffusional motion of water molecules therein; conversely, the diffusional motion of water molecules reflects tissue characteristics at the location thereof. Diffusion tensor magnetic resonance imaging (Diffusion Tensor Imaging, DTI) builds upon magnetic resonance imaging (MRI), using non-linear gradient magnetic fields in relevant directions to measure the rate of diffusion of water molecules in tissue in different directions; on this basis, a diffusion tensor of water molecules is calculated, so as to study the fine structure of the interior of tissue.
Diffusion tensor imaging of a living heart can be realized using stimulated echo (STEAM) single-shot echo planar imaging. When diffusion encoding gradients are applied at the same phase in adjacent heartbeat cycles, signal loss due to heart movement can be avoided. To prevent breathing motion from affecting the acquisition process, navigator echoes may be added before and after the STEAM sequence, wherein a navigator band is placed at the top of the diaphragm of the person being scanned.
However, a STEAM scanning method using navigator echoes in the prior art has the drawback of a lengthy scanning time.